Jean-Paul Sartre's No Exit follows the classical rules of unity, action, and place. As a one-act play, there is, of course, unity. And, with a singleness of setting, everything works towards one end, one purpose. Its existential theme is the single focus of this philosophical play as the psychological states of the characters and the objects in the room point to the symbolic significance of Sartre's work.
The inability to blink, to close one's eyes in sleep, and escape from reality, leads Garcin to utter the metaphorical remark, "So one has to live with one's eyes open all the time?" Faced with an existence stripped of all delusion, the three characters must, at last, sort out their being from the visions they have had and try to find their own existential uniqueness and define it as it will be for eternity. They cannot escape from this existential task because there is "no exit." But, since they must see themselves only in the eyes of the other without glass or mirror,
And deep down in my eyes you'll see yourself just as you want to be.
there is no way to exist as an individual. The bell, which does not always ring, represents their only connection with the outside world. The open door has been an opportunity for them to escape, but are too weak to face the consequences of freedom. Now, they are confronted for eternity with each other. The symbolic paper knife is used by Estelle in a futile attempt to escape her fate with Inez; however, she, like Garcin concludes, "Hell--is other people." They sit and ponder the consequences of their inauthentic existences in life, and their eternal inability to forge any individual essence.
I think that the exploration of character motivation is one of the most distinctive features about the play. The previous post did a great job in evoking many of these in their post. I would only add that personal conflict is something brought out in the characters' discussion throughout the play. We learn that the characters' appearance at the start of the play is nowhere near how we see them at the end of the play. Throughout the course of the drama, a significant change has been undergone in how we see them. This is brought out through dialogue and dramatic revelation of their essence. What we thought turns out to be not entirely accurate and their complexity is revealed through personal interaction. We are left with a vision of characters that each have their weaknesses. Our assessment of them is brought out through dialogue and understanding, something that makes the play all the more fascinating and philosophically profound.
No Exit is a thinly-veiled philosophical play. It relies most heavily on existential themes related to the absurdity of death and humanity's fear of freedom and choice.
The play relies heavily on symbols, imagery, and metaphor as well. The concept that "hell is other people" is represented well by these characters. Typically, we expect hell to be full of external demons and torture, but Sartre uses internal spite, fear, and anguish to carry out his subtle tortures. The main symbols in the play are doors and mirrors. The main characters refuse to exit the open door at the end, symbolic of their fear of freedom. Also, they use each other as mirrors by seeing themselves through the eyes of others. In this way, they exhibit bad faith, a false self-image projected by and through others.
Lastly, the play relies on unity. Sartre wrote the play on a dare: because of the Nazi occupation, he knew he only had four actors and no set changes, so he kept the action simple. Enotes says it best:
No Exit follows the classical rules of unity of action, time, and place. The play takes place in the length of time it takes to perform it. There is only one course of action, and everything in the setting works towards that one end. The action is also confined to one place, the drawing room. There is nothing extraneous about any aspect of the play; it is focused to one purpose.